inverse compton hard x-rays from galaxy clusters
DESCRIPTION
Inverse Compton Hard X-rays from Galaxy Clusters. Gianfranco Brunetti INAF-Istituto di Radioastronomia, Bologna, Italy Rossella Cassano Universita’ di Bologna & INAF-IRA Giancarlo Setti Universita’ di Bologna & INAF-IRA. The RE-Acceleration Model - PowerPoint PPT PresentationTRANSCRIPT
Inverse Compton Hard X-rays from Galaxy Clusters
Gianfranco Brunetti INAF-Istituto di Radioastronomia, Bologna, Italy
Rossella Cassano Universita’ di Bologna & INAF-IRA
Giancarlo SettiUniversita’ di Bologna & INAF-IRA
The RE-Acceleration Model (Brunetti et al. 2001, Petrosian 2001,…++ al.)
Turbulence
Synchrotron
ICMF Amplification
Galaxy Clusters are Lab for stochastic particle acceleration (e.g. Brunetti & Lazarian 2007)
Suitable combination of :
Beta of plasma (large)Turbulent mediaLong ion mean free path (collisionless)Large-scale magnetised systems Long time-scales
Theoretically …
Diffuse Radio Emission & in situ electron acceleration
Radio Halos are rare(Hwang 2004)
Radio Halos are always found in merging clusters(Buote 2001; Feretti 2004,05)
Radio Halos have complex spectra (spectral steepening, patchy spectral index)(Brunetti 2002,04; Petrosian 2002; Feretti et al. 2004,05; Orru’ et al. 2007)
Radio Halos are very extended(Govoni et al 2001; Brunetti 2002,04; Pfrommer & Ensslin 2004; Marchegiani et al. 2007)
Diffuse Radio Emission & origin of emitting electrons
In the RE-AccelerationScenario RH (& HXR)
should beTransient
Diffuse Radio Emission & origin of emitting electrons
In the RE-AccelerationScenario RH (& HXR)
should beTransient
Diffuse Radio Emission & origin of emitting electrons
In the RE-AccelerationScenario RH (& HXR)
should beTransient
Diffuse Radio Emission & origin of emitting electrons
GMRT(T.Venturi et al.2007;GB et al.)
Sample of 50 massive GC at z =0.2-0.4 (REFLEX + eBCS)
Similar zSimilar masses/temperatureSimilar X-ray luminosities
Diffuse Radio Emission & origin of emitting electrons
GMRT(T.Venturi et al.2007;GB et al.)
Radioloud
Radioquiet
IC HXR from the RE-Acceleration Model
Brunetti & Blasi 2005
For suitable (but viable)conditions the IC from
re-acceleratedelectrons/positrons
can match the observed HXRs
There is a big degeneracy in the synchrotron
expectations (synchrotron degeneracy)
M2
M1
Efm
~fm
vi2
v
i
ParticleAcceleration
Turbulent injection
Merging Trees
HXR: Calculations Cassano & Brunetti 2005; Cassano et al. 2006
BMb
HXR: Calculations Cassano & Brunetti 2005; Cassano et al. 2006
BMb
Luminosity Functions
Number Counts
Consequence: HXR: Results
HXR Tails (from re-accelerated electrons in Mpc regions) are produced in massive clusters,
Mvir >1015Mo
z=0.05
z=0.25
z=0.45
Luminosity Functions
Number Counts
BeppoSAX
Consequence: HXR: Results
HXR Tails (from re-accelerated electrons in Mpc regions) are produced in massive clusters,
Mvir >1015Mo
z=0.05
z=0.25
z=0.45
Luminosity Functions
Number Counts
BeppoSAX
Consequence: HXR: Results
HXR Tails (from re-accelerated electrons in Mpc regions) are produced in massive clusters,
Mvir >1015Mo
z=0.05
z=0.25
z=0.45
Simbol-X
Consequence: HXR: Results
Redshift distribution
The bulk of HXR tails from re-accelerated
particles is expected at z=0-0.2 for typical Simbol X surveys
Shallow surveys are expected to catch only local
HXR tails
F[ ]>5*10-13 cgs
F[ ]>10-13 cgs
F[ ]>10-12 cgs
ConclusionsPresently known RH are probably complex and transient (re-acceleration scenario..), they are probably just the tipof the iceberg .
Present Modelling of particle re-acceleration mayprovide first expectations for IC HXR Tails emittedfrom the re-accelerated electrons/positrons
Catching IC signals from Galaxy Clusters is important tobreak the synchrotron degeneracy (Particle-Field)
In case the HXR Tails discovered by BeppoSAX & RXTEare all real SIMBOL-X should catch HXR Tails from 10-100massive Galaxy Clusters at z=0.0-0.2
ConclusionsPresently known RH are probably complex and transient (re-acceleration scenario..), they are probably just the tipof the iceberg .
Present Modelling of particle re-acceleration mayprovide first expectations for IC HXR Tails emittedfrom the re-accelerated electrons/positrons
Catching IC signals from Galaxy Clusters is important tobreak the synchrotron degeneracy (Particle-Field)
In case the HXR Tails discovered by BeppoSAX & RXTEare all real SIMBOL-X should catch HXR Tails from 10-100massive Galaxy Clusters at z=0-0.2
Diffuse Radio Emission & origin of emitting electrons
MF is ubiquitous in GC
CRp & secondaries are ubiquitous
Miniati et al. 2001
Waves spectra
Proton spectra
Ee = 0.001 EthEp = 0.005 Eths=3.2
Kinetic Fully Non-linear Wave--Particle Coupling
(Brunetti +al. 2004; Brunetti & Blasi 2005; Brunetti & Lazarian 2007)
Electron spectra
ParticleAcceleration
Turbulent injection
Merging Trees
HXR: Calculations Cassano & Brunetti 2005; Cassano et al. 2006
Simplified Plasma Physics
&
Simplified Cosmologicalformalism (E-PS)
CR in Galaxy Clusters
CR Confinment in Galaxy Clusters(e.g., Voelk et al. 1996, Berezinsky et al. 1997)
Life-Time of hadrons ~ Hubble Time
Xm=
e.g., Schlickeiser 2002
e.g., Blasi & Colafrancesco 1999
(e.g., Blasi & Colafrancesco 1999, Dolag & Ensslin 2000, Brunetti & Blasi 2005)
Radio Emission from secondary electrons/p
Results on Upper Limits (Brunetti et al., in prep)
Results on Upper Limits (Brunetti et al., in prep)
Magnetic Field in Galaxy Clusters (Feretti+Govoni talks)
Magnetic field amplification by shear-flows driven by accretion/mergers(e.g., Dolag et al. 2002-2006, Bruggen et al. 2005)
Time scale of the decay of the field is several Gyrs (i.e., other processes come into play)(e.g., Subramanian et al. 2006)
Clarke et al. 2001
Dolag 2006
Vogt & Ensslin 2005
A Radio-Based Approach
Pro : Deep radio data available
- Deep observations at low frequencies - in 2-3 years (LOFAR)
Contro : -Secondaries (e.g., Blasi & Colafrancesco 1999, Dolag & Ensslin 2000)
- Shock Acceleration (e.g., Sarazin 1999, Dermer & Berrington 2005) - Stochastic Acceleration (e.g., Schlickeiser et al. 1987)
- Stochastic RE-Acceleration (e.g., Brunetti et al. 2001, Petrosian 2001, ...)
A Radio-Based Approach
Pro : Deep radio data available
- Deep observations at low frequencies - in 2-3 years (LOFAR)
Contro : -Secondaries (e.g., Blasi & Colafrancesco 1999, Dolag & Ensslin 2000)
- Shock Acceleration (e.g., Sarazin 1999, Dermer & Berrington 2005) - Stochastic Acceleration (e.g., Schlickeiser et al. 1987)
- Stochastic RE-Acceleration (e.g., Brunetti et al. 2001, Petrosian 2001, ...)
Results I: Origin of the emitting electrons (Brunetti et al., in prep)
Region of non
Radio-emitting
massive clusters
Present RH are inconsistent with the scenario of secondary electrons
z > 0.2
A Radio-Based Approach
How to disentangle the contributions from re-accelerated and from secondary particles ?
NCR Nth
e B Synchrotron
Results II: Limits on CR in Galaxy Clusters (Brunetti et al., in prep)
Bsynchrotron
=2.1-2.3(M=3.8-6.4)
=2.9-3.3(M=2-2.3)
Simulations
1
Results II: Limits on CR in Galaxy Clusters (Brunetti et al., in prep)
Bsynchrotron
=2.1-2.3
=2.9-3.3
e- p+
e- e+
The Re-acceleration Model
The RE-Acceleration ModelBrunetti et al. 2001; Petrosian 2001Ohno et al. 2002; Kuo et al. 2003; Fujita, Takizawa, Sarazin 2003;Brunetti et al. 2004; Brunetti & Blasi 2005; Cassano & Brunetti 2005; Brunetti & Lazarian 2007
Turbulence
Diffuse Radio Emission & origin of emitting electrons
Region of non
Radio-emitting
massive clusters
Turbulence
e- p+
e- e+
The Re-acceleration Model
Shocks
e- p+
Turbulence
e- p+
e- e+
The Re-acceleration Model
Shocks
e- p+
Turbulence
e- p+
e- e+
The Re-acceleration Model
Shocks
e- p+
Pfrommer & Ensslin 2004
Emission from CR in Galaxy Clusters
Radio Emission from secondary electrons/p
Miniati et al. 2001Dolag 2004
CR Confinement & accumulation + ubiquitous & slow decay of B (Dolag 2006; Subramanian et al. 2006)
Radio Halos cannot be transient phenomena
Similar GC should have (statistically) similar RH
Diffuse Radio Emission & origin of emitting electrons
Radio Halos are always found in merging clusters(Buote 2001; Feretti 2004,05)
Diffuse Radio Emission & origin of emitting electrons
Radio Halos have complex spectra (spectral steepening, patchy spectral index)(Brunetti 2002,04; Petrosian 2002; Feretti et al. 2004,05; Orru’ et al. 2007)
Thierbach +al. 2002
Orru’ et al. 2007
Diffuse Radio Emission & origin of emitting electrons
Radio Halos are very extended(Govoni et al 2001; Brunetti 2002,04; Pfrommer & Ensslin 2004; Marchegiani et al. 2007)
Brunetti 2004Govoni et al.,2001
R X0.6
Searching for RH with GMRT at 610 Mhz (Giacintucci et al. 2006; Venturi et al. 2007; …)
Sample of 50 massive GC at z =0.2-0.4 (REFLEX + eBCS)
Observations of ~30 GC at GMRT (610 MHz) down to brightness rms ~ 0.03-0.1 mJy/beam
Detection rate of diffuse radio emission 20%
Uppe
r
limits
CR Confinment for cosmological time-scalesenhances the possibility ofp-p collisions in the ICM
a) -rays from o decay
b) Synchrotron from e±
c) IC from e±
Emission from CR in Galaxy Clusters
Protons arethe dominant
CR populationin Clusters
(Voelk et al.1996; Berezinsky et al. 1997)
Blasi, Gabici, Brunetti,2007
CR Confinment for cosmological time-scalesenhances the possibility ofp-p collisions in the ICM
a) -rays from o decay
b) Synchrotron from e±
c) IC from e±
Emission from CR in Galaxy Clusters
Protons arethe dominant
CR populationin Clusters
(Voelk et al.1996; Berezinsky et al. 1997)
Blasi, Gabici, Brunetti,2007
Outline
Why Re-Acceleration ??
Re-Acceleration Model
HXR emission & Simbol X